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Chapter 1 Β  Β  Anatomy I: Β  Body Segments, Joints and Muscles



Table of ContentsΒΆ

Body Segments: Bones, segments and groupsΒΆ

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A typical human body has approximately 200 bones. In this textbook, only approximately 10 bones will be discussed.


Instead of focussing on individual bones, this textbook will focus primarily on segments. Nevertheless, to understand segments, it is important to know which bones belong to which segments.



  • Bones:
    • A bone is a close-to-rigid structure in our body to which muscles and/or other soft tissues attach.
    • Bones define our bodies' overall structure.
    • Bones transmit forces.
    • Specific anatomical terms exist for all bones.


  • Segments:
    • A segment consists of a bone and its surrounding soft tissue.
    • A segment's soft tissue can move with respect to the segment's bone.
    • Intra-segment soft tissue movement is usually much smaller than than inter-segment movement.


  • Groups:
    • A group is a collection of multiple bones or multiple segments


  • In Biomechanics:
    • Bone names, segment names and group names are all commonly used.
    • If someone says the anatomical bone name (e.g. "humerus"), they are usually referring to the bone, and not to the segment.
    • If someone uses the common English name (e.g. "upper arm"), they are usually referring to the segment, and not to the bone.


  • This course will deal primarily with segments and groups, but will also occasionally use bone names.




Upper limbΒΆ

bones_arm



Bone name [anatomical] Common English name Type
Scapula Shoulder OR Shoulder Blade Bone & Segment
Humerus Upper Arm Bone & Segment
Radius (None) Bone
Ulna (None) Bone
Radius & Ulna Lower Arm OR Forearm Segment & Group
Humerus & Radius & Ulna Arm OR Upper Limb Group
Scapula & Humerus & Radius & Ulna & (hand and wrist bones) Upper Limb Group



Lower limbΒΆ

bones_leg



Bone name [anatomical] Common English name Type
Femur Thigh OR Upper Leg Bone & Segment
Tibia Shin Bone
Fibula (None) Bone
Calcaneus Heel Bone
Tibia & Fibula Lower Leg OR Shank Segment & Group
Calcaneus & (other foot bones) Foot* Segment & Group
Femur & Tibia & Fibula Leg Group
Femur & Tibia & Fibula & Calcaneus & (other foot bones) Lower Limb Group


*In Biomechanics, the foot is often modeled as a single rigid segment.



TrunkΒΆ

bones_trunk



Bone name [anatomical] Common English name Type
Vertebra* Back bone Bone
Pelvis Hip Bone
Sacrum (None) Bone
Illium (None) Bone
Illium & Sacrum Pelvis Segment
Vertebral column Spine OR Backbone Group
Trunk OR Torso Trunk Group & Segment*


*"Vertebrae" is the plural of "vertebra" (i.e., one vertebra and two vertebrae).

*In Biomechanics, the trunk is often modeled as a single rigid segment, especially when modeling movements without much vertrbral column flexion (e.g. walking).



Joints: Main inter-segment jointsΒΆ

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A joint allows for relative motion between bones. Joints are anatomical structures, and are usually comprised of cartilage, ligaments, tendons and other soft tissues.

The main joints considered in this textbook are the six listed in the table below.

These joints are indicated in blue font in the figures above.

Joint name Proximal bone Distal bone
Shoulder Scapula Humerus
Elbow Humerus Radius & Ulna
Wrist Radius & Ulna (multiple wrist bones)
Hip Sacrum Femur
Knee Femur Tibia & Fibula
Ankle Tibia & Fibula Talus & (other foot bones)



Muscles: Main muscles and muscle groupsΒΆ

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A typical human body contains over 600 muscles.


This textbook will consider only muscle groups, and not individual muscles.


The six main muscle groups that will be considered in this textbook are indicated below.



muscles



Common muscle group name Joint(s) Main muscles [anatomical names]
Pectoralis Shoulder Pectoralis major, etc.
Biceps Shoulder & Elbow Biceps brachii, etc.
Triceps Shoulder & Elbow Triceps brachii, etc.
Quadriceps Hip & Knee Vastus, etc.
Hamstrings Hip & Knee Biceps femoris, etc.
Calf Knee & Ankle Gastrocnemius, etc.



SummaryΒΆ

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  • This chapter has described the main bones, segments, joints and muscles of the human body
  • Bones are near-rigid objects.
  • Segments consist of one or more bones and their surrounding soft tissue.
  • In Biomechanics, bones, segments, and muscles are often referred to using both common English terms and anatomical terms.
  • This main anatomical structures considered in this textbook are those described in this chapter: approximately 10 bones / segments, approximately 6 joints, and approximately 6 muscle groups.